NAME

visudo - edit the sudoers file

SYNOPSIS

visudo [ -c ] [ -fsudoers ] [ -q ] [ -s ] [ -V ]

DESCRIPTION

visudo edits the sudoers file in a safe fashion, analogous
to vipw(8). visudo locks the sudoers file against multiple
simultaneous edits, provides basic sanity checks, and checks
for parse errors. If the sudoers file is currently being
edited you will receive a message to try again later.
There is a hard-coded list of editors that visudo will use
set at compile-time that may be overridden via the editorsudoers Default variable. This list defaults to the path to
vi(1) on your system, as determined by the configure script.
Normally, visudo does not honor the VISUAL or EDITOR
environment variables unless they contain an editor in the
aforementioned editors list. However, if visudo is config-
ured with the --with-enveditor flag or the enveditor Default
variable is set in sudoers, visudo will use any the editor
defines by VISUAL or EDITOR. Note that this can be a secu-
rity hole since it allows the user to execute any program
they wish simply by setting VISUAL or EDITOR.
visudo parses the sudoers file after the edit and will not
save the changes if there is a syntax error. Upon finding
an error, visudo will print a message stating the line
number(s) where the error occurred and the user will receive
the "What now?" prompt. At this point the user may enter
"e" to re-edit the sudoers file, "x" to exit without saving
the changes, or "Q" to quit and save changes. The "Q"
option should be used with extreme care because if visudo
believes there to be a parse error, so will sudo and no one
will be able to sudo again until the error is fixed. If "e"
is typed to edit the sudoers file after a parse error has
been detected, the cursor will be placed on the line where
the error occurred (if the editor supports this feature).

OPTIONS

visudo accepts the following command line options:
-c Enable check-only mode. The existing sudoers file will
be checked for syntax and a message will be printed to
the standard output detailing the status of sudoers. If
the syntax check completes successfully, visudo will
exit with a value of 0. If a syntax error is encoun-
tered, visudo will exit with a value of 1.
-f Specify and alternate sudoers file location. With this
option visudo will edit (or check) the sudoers file of
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your choice, instead of the default, /etc/sudoers. The
lock file used is the specified sudoers file with ".tmp"
appended to it.
-q Enable quiet mode. In this mode details about syntax
errors are not printed. This option is only useful when
combined with the -c flag.
-s Enable strict checking of the sudoers file. If an alias
is used before it is defined, visudo will consider this
a parse error. Note that it is not possible to dif-
ferentiate between an alias and a hostname or username
that consists solely of uppercase letters, digits, and
the underscore ('_') character.
-V The -V (version) option causes visudo to print its ver-
sion number and exit.

ENVIRONMENT

The following environment variables are used only if visudo
was configured with the --with-env-editor option:
VISUAL Invoked by visudo as the editor to use
EDITOR Used by visudo if VISUAL is not set

FILES

/etc/sudoers List of who can run what
/etc/sudoers.tmp Lock file for visudo

DIAGNOSTICS

sudoers file busy, try again later.
Someone else is currently editing the sudoers file.
/etc/sudoers.tmp: Permission denied
You didn't run visudo as root.
Can't find you in the passwd database
Your userid does not appear in the system passwd file.
Warning: undeclared Alias referenced near ...
Either you are using a {User,Runas,Host,Cmnd}_Alias
before defining it or you have a user or hostname listed
that consists solely of uppercase letters, digits, and
the underscore ('_') character. If the latter, you can
ignore the warnings (sudo will not complain). In -s
(strict) mode these are errors, not warnings.
Warning: runas_default set after old value is in use ...
You have a runas_default Defaults setting listed in the
sudoers file after its value has already been used.
This means that entries prior to the runas_default set-
ting will match based on the default value of
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runas_default (root) whereas entries after the
runas_default setting will match based on the new value.
This is usually unintentional and in most cases the
<runas_default> setting should be placed before any
Runas_Alias or User specifications. In -s (strict) mode
this is an error, not a warning.

SEE ALSO

AUTHOR

Many people have worked on sudo over the years; this version
of visudo was written by:
Todd Miller
See the HISTORY file in the sudo distribution or visit
http://www.sudo.ws/sudo/history.html for more details.

CAVEATS

There is no easy way to prevent a user from gaining a root
shell if the editor used by visudo allows shell escapes.

BUGS

If you feel you have found a bug in visudo, please submit a
bug report at http://www.sudo.ws/sudo/bugs/

SUPPORT

Commercial support is available for sudo, see
http://www.sudo.ws/sudo/support.html for details.
Limited free support is available via the sudo-users mailing
list, see http://www.sudo.ws/mailman/listinfo/sudo-users to
subscribe or search the archives.

DISCLAIMER

Visudo is provided ``AS IS'' and any express or implied war-
ranties, including, but not limited to, the implied warran-
ties of merchantability and fitness for a particular purpose
are disclaimed. See the LICENSE file distributed with sudo
or http://www.sudo.ws/sudo/license.html for complete
details.
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